Number Of CH2 Groups Research Articles

Polymers of Carbonic Acid. 20. High Molecular Weight Poly(Decamethylene Carbonate) by Ring-Opening Polymerization Initiated with BuSnCl3 or SnOct2

Cyclobis(decamethylene carbonate), (DMC)2, was prepared by polycondensation of 1,10-decane diol and diethylcarbonate followed by thermal depolymerization in vacuo. Two series of polymerizations were conducted in bulk at 120°C with BuSnCl3 as initiator. Either the reaction time was varied at a constant monomer/initiator (M/I) ratio or the M/I ratio was varied at constant reaction time. Two analogous seires of polymerizations were conducted with Sn(II)-2-ethylhexanoate, SnOct2. Both initiators showed almost equal reactivities, but the highest yields (up to 98%) and the highest molecular weights (M w up to 88,000) were obtained with BuSnCl3. Both initiators yielded polyDMC free of ether groups. DSC measurements revealed that polyDMC is a rapidly crystallizing material with a melting temperature (T m) of 67 ± 1°C. A comparison with poly(alkylene carbonate)s having fewer CH2 groups demonstrated that the rate of crystallization increases with an increasing number of CH2 groups.

Adsorption of Cationic Surfactants on Rutile

The adsorption and zeta potential of two series of cationic surfactants, i.e. alkyltrimethylammonium bromide and alkylpyridinium chloride, on rutile have been studied. The two series varied only in their hydrocarbon chain length. The effect of chain length on the lateral two-dimensional aggregation phenomena of surfactant molecules on the rutile surface has been explained by evaluating various thermodynamic parameters such as the effective number of CH2 groups removed from the aqueous environment on to the solid surface (dn/d In C), the mean cohesive energy per CH2 group (Φ) and the average mean aggregation number of the hemimicelle (nhm). The value of the mean cohesive energy in the case of alkyltrimethylammonium bromide (0.599 kcal/mol) is in very good agreement with literature values. It supports hemimicellar formation.

Effect of β-Cyclodextrin on the Excited State Properties of 3-Substituted Indole Derivatives

The effect of β-cyclodextrin on the absorption and fluorescence spectra of 3-R-indoles (R = CH3 or (CH2)nCOOH with n = 1, 2 and 3) was studied. The inclusion in β-cyclodextrin barely changed the UV spectra, while significant variations were produced in the emission spectra, particularly regarding the fluorescence quantum yields. These changes, which are pH dependent, allow the determination of the association equilibrium constants (kAssoc) under different sets of conditions. For the derivatives with R = (CH2)nCOOH, the kAssoc at pH = 2 increased linearly with the number of CH2 groups. The changes in fluorescence quantum yield are higher for the neutral than for the ionized compounds due to greater changes in the nonradiative rates of the neutral species when it is un-ionized.

13C NMR chemical shifts of unbranched alk‐2‐yn‐1‐ols, ω‐alkyn‐1‐ols and ‘internal’ alkyn‐1‐ols

Abstract13C NMR chemical shifts of three types of unbranched alkyn‐1‐ols were measured and assigned: alk‐2‐yn‐1‐ols, ω‐alkyn‐1‐ols and ‘internal’ alkyn‐1‐ols. The derived OH shift increments depend on the number of CH2 groups between the triple bond and the OH group.

Iron acquisition by Mycobacterium tuberculosis: isolation and characterization of a family of iron-binding exochelins.

Mycobacterium tuberculosis, the primary agent of tuberculosis, must acquire iron from the host to cause infection. To do so, it releases high-affinity iron-binding siderophores called exochelins. Exochelins are thought to transfer iron to another type of high-affinity iron-binding molecule in the bacterial cell wall, mycobactins, for subsequent utilization by the bacterium. In this paper, we describe the purification of exochelins of M. tuberculosis and their characterization by mass spectrometry. Exochelins comprise a family of molecules whose most abundant species range in mass from 744 to 800 Da in the neutral Fe(3+)-loaded state. The molecules form two 14-Da-increment series, one saturated and the other unsaturated, with the increments reflecting different numbers of CH2 groups on a side chain. These series further subdivide into serine- or threonine-containing species. The virulent M. tuberculosis Erdman strain and the avirulent M. tuberculosis H37Ra strain produce a similar set of exochelins. Based on a comparison of their tandem mass spectra, exochelins share a common core structure with mycobactins. However, exochelins are smaller than mycobactins due to a shorter alkyl side chain, and the side chain of exochelins terminates in a methyl ester. These differences render exochelins more polar than the lipophilic mycobactins and hence soluble in the aqueous extracellular milieu of the bacterium in which they bind iron in the host.

Salting-out thin layer chromatography of transition metal complexes: A comparative study of the effect of increased number of CH2 groups in chelate rings

The regularities previously established in salting-out thin-layer chromatography on silica gel of Co(III) complexes, in which the side chains of a specific chelate ring were successively increased in length, were also found to be valid for two series of Co(III) complexes of the EDTA type, in which different chelate rings were enlarged by one CH2 group. It was found that in the case of complexes of the EDTA type the salting-out efficiencies were practically the same for all members of a series, while the values of the separation factors were paractically independent of the ammonium sulphate concentration in the solvent system used. The results obtained were consistent with the mechanism of nonspecific hydrophobic interactions. The method used can be applied to the separation of the members of the series of complexes that we investigated.

Rate constants for Hydrogen abstraction reactions of NO3 in aqueous solution

AbstractRate constants have been measured by pulse radiolysis for the reactions of the NO3 radical with five cyclic ethers and a series of alcohols. Rate constants ranged from 3.5 × 104 M×1 s×1 for deuterated methanol to 1.1 × 107 M−1 s−1 for tetrahydrofuran. The rate constants for the reactions of NO3 with the alcohols 1‐propanol to 1‐heptanol were found to be linearly dependent on the number of CH3 groups with a group reactivity of 6.4 × 105 M−1 s−1.

Near infrared spectra of caffeine and its related compounds and their application to determination of caffeine content in green tea.

Near infrared reflectance spectra of caffeine and its related compounds such as xanthine, theophylline and theobromine were studied in connection with their chemical structures. A major difference in the spectra was characterized with a difference in the number of CH3 groups contained in the compounds. It has been verified that the near infrared reflectance spectroscopy can be applied to the quantitative analysis of caffeine in green tea.

Heat capacities of polyethylene and linear aliphatic polyoxides

Heat capacities at constant pressure and volume are calculated from full and partially approximated normal mode frequency spectra for crystalline polyethylene, poly(oxymethylene), poly(oxyethylene), poly(oxytrimethylene), poly(oxytetramethylene), poly(oxyoctamethylene), poly(oxymethyleneoxyethylene), and poly(oxymethyleneoxytetramethylene). A calculation scheme using a Tarasov-function for 2 N skeletal modes and approximation of the residual normal modes from known data on polyethylene and poly(oxymethylene) is developed for all homologous, linear, aliphatic polyoxides. N is the number of CH 2-groups in the repeating unit. Calculations can be carried out over the whole temperature range OK to melting. For θ-temperatures and constant A o for the C v− to − C p conversion, oxygenconcentration dependent curves are given. Recommended experimental data bank heat capacities agree to ±5% or better.

Chromatography of diols. Regularities in the retention of linear diprimary diols in gas-solid and gas-liquid chromatography

Using various sorbents in gas-liquid chromatography and gas-solid chromatography, the dependence of the retention of diprimary linear diols of the HOCH2(CH2)nCH2−OH type (n=0–4) on different parameters characterizing the physicochemical properties of the diols was studied. As shown, the relationship between the logarithm of the retention volume, or the boiling point, molecular mass, number of CH2-groups, density, refractive index, molecular refraction, and the logarithm of the retention volumes obtained on another stationary phase is either linear or nearly linear. The linear regression coefficients of the various relationships are given.

Structural studies on molecular complexes of polyethers, 3. Urea‐polyether complexes

AbstractComplexes of urea with polyethers, \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{‐‐} [\left( {{\rm CH}_2 } \right)_m {\rm O\rlap{‐‐} ]}_n$\end{document} (m = 2–4, 6, 8–10), were prepared, and their crystal structures and decomposition temperatures were studied. The crystal structures of the complexes with polyethers (m ≥ 3) are similar to those of n‐alkanes, so‐called urea adducts. Only poly(oxyethylene), (m = 2), presents a complex of a different type of crystal structure. The decomposition temperatures of the complexes are in the range of 134 to 144°C and change in parallel with the melting points of polyethers themselves against the number of CH2 groups in the monomeric units.

Methotrexate analogues. 20. Replacement of glutamate by longer-chain amino diacids: effects on dihydrofolate reductase inhibition, cytotoxicity, and in vivo antitumor activity.

Chain-extended analogues of methotrexate were synthesized by condensation of 4-amino-4-deoxy-N10-methylpteroic acid with esters of L-alpha-aminoadipic, L-alpha-aminopimelic, and L-alpha-aminosuberic acids, followed by ester hydrolysis with acid or base. Coupling was accomplished in up to 85% yield by the use of the peptide bond forming reagent diethyl phosphorocyanidate at room temperature. The products were found to bind bacterial (Lactobacillus casei) and mammalian (L1210 mouse leukemia) dihydrofolate reductase with an affinity comparable to methotrexate and were also equitoxic to L1210 cells in culture. Cytotoxicity increased up to 3-fold as the number of CH2 groups in the amino acid side chain was extended from two to five. The alpha-aminoadipate and alpha-aminopimelate analogues were poor substrates for carboxypeptidase G1, confirming that this enzyme has a strict requirement for a C-terminal L-glutamic acid residue. The in vivo antitumor activity of the chain-extended analogues against L1210 leukemia in mice was comparable to that of the parent drug on the qd X 9 schedule, but higher doses were required to achieve the same increase in survival. The results were consistent with findings, reported separately, that these compounds are poor substrates for folate polyglutamate synthetase and therefore would not be expected to form gamma-polyglutamates once they enter a cell. This distinctive property has potential therapeutic implications for the treatment of certain MTX-resistant tumors whose resistance may be associated with a lower than normal capacity to form gamma-polyglutamates in comparison with proliferative tissues such as intestinal mucosa or marrow.

The physical crosslinking of polyurethane elastomers studied by X-ray investigation of model urethanes

Polyurethane elastomers extended with aliphatic glycols or diamines, show a characteristic fluctuation in their thermal and hydrothermal properties which is dependent on the number of CH2 groups in the chain extender (“even” or “odd”).

The double layer and ion adsorption at the interface between two immiscible solutions Part III. Long chain alkyl-trimethylammonium halides at partition equilibrium between water and nitrobenzene

The surface excesses of alkyltrimethylammonium halides have been evaluated from interfacial surface tension measurements carried out at the partition equilibrium between water and nitrobenzene. The model considered is constituted by two space charge layers on either side of a central compact layer which contains alkyltrimethylammonium ions arranged as in an adsorbed monolayer. The value of the electrical potential at the junction plane between the two phases depends on the degree of dissociation within the inner layer and on the number of specifically adsorbed ions. If one assumes complete dissociation it is possible to establish the variation of the adsorption isotherms with the chemical and electrical parameters and thus determine the value of the free energy of adsorption with the number of CH2 groups in the alkyl chain. The results obtained do not indicate an important effect due to the counter ion, which would tend to substantiate the hypothesis of a total dissociation within the central layer. Furthermore the fact is stressed that the knowledge of the isotherm depends on the magnitude of the potential drop within the compact layer, the value of which cannot be determined by purely thermodynamical measurements.

Determination of the degree of branching in polyethylene by an i.r. method of decomposition of bands

The degree of branching (number of CH3 groups per 100 carbon atoms) of a series of commercial samples of polyethylene crystallized from the melt has been determined by i.r. spectroscopy using a method of band decomposition by means of a computer programme. For this purpose the spectral region 1320–1400 cm−1 was investigated. The absorption coefficient value for the CH3 symmetric deformation mode agrees very well with the value obtained by Willbourn using the compensation method [9].

2-(Trialkoxysilylalkylthio)ethyl vinyl sulfides

Trialkoxysilylalkanethiols (CH3O)3Si(CH2)nSH (n=1–3) react with divinyl sulfide at 100–110° to give 2-(trialkoxysilylalkylthio)ethyl vinyl sulfides (CH3O)3Si(CH2)nS (CH2)2SCH=CH2 in high yield. The reactivity of the trialkoxysilylalkanethiols decreases with increase in the number of CH2 groups between the S and Si atoms. A second molecule of the organosilicon thiol acids adds with difficulty to divinyl sulfide to give the diadduct.

INTERFACIAL RESISTANCE IN LIQUID-LIQUID MASS TRANSFER

The interfacial processes between aqueous and organic phases for mass transfer of carboxylic acids were clarified using the cylindrical-lens schlieren apparatus. There existed no detectable interfacial resistance for acetic acid as a solute, while for n-valeric acid, interfacial resistance played an important role in the mass transfer. For the transfer of carboxylic acids, an equilibrium was attained between the concentration in the aqueous phase next to the interface and that at the interface. The process between organic phase and the interface was the rate-determining step among the processes associated with the interface. The interfacial resistance was found to originate from the resolvation process and the entropy effect of the solute transferring from the interface to the organic phase, the latter being affected by the number of CH2 groups in the solute molecule.

THE EFFECT OF WEAK MOLECULAR INTERACTIONS ON SELECTIVE FORMATION OF UNSYMMETRICAL BISSULFIDES

Abstract As part of a continuing study on synthetic control, some investigations are made on the effect of two factors, the number of CH2 groups (m and n) and changes in weak molecular interactions between a pair of model compounds (1 and 2), on the selective formation of an unsymmetrical bissulfide (4).

Reaction of S-(?-ethylmercaptoalkyl) diphenyl thiophosphinates, O-(?-ethylmercaptoalkyl) diphenyl phosphinates, and their methiodides with cholinesterase from horse blood serum

1. We determined the kinetic constants for the combined inhibition of butyrylcholinesterase by diphenyl thiophosphinates (C6H5)2P(O)S(CH2)nSC2H5 and their methiodides\((C_6 H_5 )_2 P(O)S(CH_2 )n\mathop S\limits^ \oplus (CH_3 )C_2 H_5 \cdot I^-- \), with n=2–6, and also the reversible inhibition constants for the analogous oxygen esters. 2. The ability of diphenyl thiophosphinates, diphenyl phosphinates, and their methiodides, to undergo reversible sorption on the active surface of the enzyme is enhanced with increase in the number of CH2 groups. In the sulfide series of thioesters the irreversible inhibition rate constants remain practically unchanged with increase in the number of CH2 groups, while in the sulfonium series they decrease symbatically with decrease in their alkaline hydrolysis rate constants.

Synthesis of monovinyl silanes with different aliphatic substituents on the silicon atom

1. A number of vinyl derivatives of silicon with different aliphatic substituents has been synthesized. 2. It has been shown possible to evaluate spectroscopically the number of CH2 groups in the longchain radical (R).